Neytiri, voiced by Zoe Saldana, is one of the Na'vi race of beings in 'Avatar.' Writer and director James Cameron helped create whole new language for the Na'vi in an effort to make the story believable.

Even for a film set in outer space, "Avatar's" ability to defy gravity has confounded the movie industry.

For Hollywood, even the most successful films see their box-office take drop by 50 percent after the first week. In its fourth week, however, "Avatar" earned $48 million, marking its fourth straight week as the top-grossing film in the US and still only 37 percent off its first week draw ($77 million).

It creates a unique 1-2 for "Avatar" writer and director James Cameron. Already, he is the writer and director of the two top-grossing movies of all-time worldwide. His last movie before "Avatar," "Titanic," is No. 1 with $1.8 billion. With $1.3 billion so far, "Avatar" displaced "Lord of the Rings: Return of the King" as No. 2 worldwide this weekend.

Movies made for the big screen

Mr. Cameron's formula is no secret: a heavy dose of Hollywood. But in a business forever trying to outdo itself, where special effects have made annihilating entire worlds as mundane as opening a bag of chips, Cameron's success is instructive.

In short, he makes films made for theaters – must-see movies so overwhelming to the senses that even Blu-Ray can never do it justice.

And for Cameron, it is also the triumph of the story behind the story. For "Avatar," Cameron helped create a new language and write a 350-page encyclopedia of the science and culture of his fictional world Pandora.

"There aren't many examples of fully detailed worlds in the movies," Cameron told USA Today. "You've got the Tolkien [Lord of the Rings] universe, the Gene Roddenberry [Star Trek] universe, the 'Star Wars' universe. You can't compete with that kind of lore, but what we can do is give the illusion that there's that kind of depth and detail."

The 3-D factor

Moviemaking Cameron-style is not for executives who are faint of heart. Unofficial estimates suggest the film cost at least $430 million to make and market. But Cameron's experiments often bring his studio financial reward in the end.

Much of Cameron's 12-year hiatus between "Titanic" and "Avatar" was spent learning – and inventing – the tools to shoot a groundbreaking movie in 3-D. "I was learning a craft and trade of 3-D production, gearing up." Cameron told USA Today. "Whatever movie I was going to make, it was going to be in 3-D."

New data show that 3-D is driving "Avatar's" strong staying power at the box office. Some 80 percent of the movie's receipts for this past weekend came from 3-D screens, The Los Angeles Times reports. On opening weekend, that figure was 71 percent.